The relationship of microorganisms to the etiology of destructive periodontal disease has been established. The purpose of the present investigation is to determine which microorganisms are associated with various forms of destructive disease. The predominant cultivable microbiota in individual sites demonstrating active destruction during clinical monitoring will be determined using comprehensive morphologic and biochemical characterization techniques. The effect of therapy (either mechanical and/or chemotherapeutic) on the composition of the microbiota will be determined. The patients will continue to be monitored longitudinally to determine the rate of recolonization of suspected pathogens. Concomitant monitoring of clinical status will also be carried out in order to reveal relationships of the microbiota to progress of disease.